Integrated circuits fabricated in silicon-on-insulator ("SOI") substrates offer various performance advantages. A commercially fabricated silicon-on-insulator wafer may be generally classified into one of two types. A SIMOX (separation by implanted oxygen) wafer is one type which generally includes an oxide layer in a bulk wafer which is obtained by implanting oxygen ions in the bulk wafer and then annealing the wafer. The second type is a bonded SOI wafer which may be produced by forming a thermal oxide layer on the surface of a bulk wafer and then directly bonding a device wafer on the thermal oxide layer.
In the case of the bonded SOI wafer, if impurity particles exist in the interface between the bulk wafer and the device wafer after the bonding process, the device may be useless commercially. Therefore, the bonding process is generally performed in a super-clean room in order to attempt to prevent the interface between the bulk wafer and the device wafer from being contaminated by impurity particles. However, in practice, it is generally not possible to carry out a bonding process without generating some impurity particles. Therefore, in some cases, impurity particles exist in the interface between the wafers after bonding the device wafer to the bulk wafer. As a result, if impurity particles exist, a debonding process may be provided to allow removal of the impurity particles.
FIGS. 1A and 1B are cross-sectional views illustrating a conventional wafer debonding method. As illustrated in FIG. 1A, after forming thermal oxide layer 30 on bulk wafer 10, device wafer 20 is directly bonded on thermal oxide layer 30 to form bonded wafer 60. If it is determined that impurity particles exist in the interface between bulk wafer 10 and device wafer 20 requiring debonding, razor blade 40 is inserted between bulk wafer 10 and device wafer 20, and the bonded wafers are debonded manually by hands 50 as shown in FIG. 1B.
With the conventional method of debonding as illustrated in FIGS. 1A and 1B, while the thickness of each of bulk wafer 10 and device wafer 20 is thin, the bonding strength between the wafers is typically too strong to separate the wafers with bare hands alone. Therefore, razor blade 40 is inserted as an auxiliary tool for debonding bonded wafer 60.
However, razor blade 40 may cause undesirable scratches around edges of bulk wafer 10 and device wafer 20, causing a scratch in the surfaces of the wafers. Since this scratch typically can not be eliminated even if the debonded wafers are rebonded after cleaning, the wafers having a scratch may need to be discarded, thereby increasing processing costs.